GeoEye Inc. made a public, $792 million buyout offer for rival satellite company DigitalGlobe Inc. on Friday after private merger talks between the companies fell apart.

Both companies — the two U.S. commercial providers of unclassified high-resolution satellite imagery — have significant Denver-area operations. DigitalGlobe (NYSE: DGI) is based in Longmont. Herndon, Va.-based GeoEye Inc. (Nasdaq: GEOY) employs about 130 people in Thornton.

GeoEye surprised observers by publicly making what it called a “friendly” stock and cash offer to buy DigitaGlobe shares.

Under the proposed offer, DigitalGlobe shareholders would get the equivalent of $17 a share, including $8.50 cash and $8.50 in GeoEye stock.

The offer represents a 26 percent premium on DigitalGlobe’s closing share price on Thursday, GeoEye said. GeoEye’s board is also willing to consider a different ratio of stock and cash, or even make an all-cash bid, to complete a purchase if necessary, the company said.

Matt O’Connell, GeoEye CEO, said on a conference call with analysts that the companies had discussed a straight merger in the hope of becoming a more efficient, joint operation in an era of tighter U.S. government budgets. The government is the largest buyer of bother companies’ images.

DigitalGlobe recently broke off merger talks between the companies without explanation, O’Connell said, and GeoEye now wants DigitalGlobe’s shareholders to know about and consider the buyout offer for themselves.

DigitalGlobe’s board is reviewing GeoEye’s offer and will “pursue the course of action that is in the best interests of DigitalGlobe and its stockholders,” DigitalGlobe said in a statement. It advised its investors not to take any action.

The company declined to comment further.

Combining GeoEye and DigitalGlobe would create a company that’s financially more efficient and better positioned to serve its customers — primarily military, intelligence and disaster relief agencies, O’Connell said.

Among other things, a merged company would have to build one less satellite than they currently plan separately, which could save hundreds of millions of dollars while providing the U.S. government the same level of service, he said.

“Money is going to be tight in this country for a while,” O’Connell said. “This is great way to help the government, to help our warfighters, to help the taxpayers and for investors to do well.”

In a letter Friday to DigitalGlobe CEO Jeffrey Tarr, O’Connell quotes Tarr as saying in a March 2 letter that “...a well-managed combined company would enjoy material scale and scope benefits in addition to significant cost savings and would be well positioned to meet the needs of the U.S. Government and other customers.”

Both DigitalGlobe and GeoEye found out this week that the National Geospatial-Intelligence Agency, the U.S. government agency that buys most of the companies’ images, plans to fully fund each business’ contract under the NGA’s EnhancedView program.

That was big news for both businesses. Rumors had swirled in recent weeks that the 10-year, $7.3 billion EnhancedView program could, like many parts of federal spending, be slashed.

DigitalGlobe receives up to $250 million annually from its NGA contract. GeoEye receives a maximum of $150 million annually under EnhancedView.

There had been questions whether GeoEye would get the money this year, and it moved up its quarterly conference call to Friday to announced its NGA news in tandem with its offer for DigitalGlobe.

“We wanted to reassure our our investors and employees we continue to have a very positive relationship with the NGA,” O’Connell said.

DigitalGlobe added more than 100 new positions in 2010 and again in 2011. It now employs about 700 people worldwide, with about 600 of them at its Longmont headquarters.